Building upon our example from the previous episode, let's now figure out how we might record changes to our models. For example, if a user updates the title of a particular document, let's learn how to also record/track the old and new title, in the process.

If you only need to check one or two parameters from the query string to filter a bit of data, performing that logic in the controller is simple enough. But now imagine an e-commerce site, where there are dozens of ways to filter the data. What else might be possibility?